Thermosensitivity of preoptic neurones in a hibernator at high and low ambient temperatures.

The effect of ambient temperature on the thermosensitivity of preoptic neurones was studied in euthermic golden hamsters. At skin temperatures (Tsk) of 20 degrees C, preoptic units were still responsive to hypothalamic temperatures (Thy) below 10 degrees C, while at Tsk = 36 degrees C these neurones became inactive at Thy = 15 degrees C on the average. These studies suggest that thermoreceptive preoptic neurones, influenced by a high activity of cutaneous cold-receptors, are capable of sensing core temperatures even in deep hibernation.